题目传送门：

　　这道题直接模拟就好了

　　

/*ID:abc31261LANG:C++TASK:fence*/#include
     
      #include
      
       #include
       
        #include
        
         using namespace std;const int maxn=600,n=500;vector
         
           g[maxn];int r[maxn],road[maxn],num=0,f[maxn][maxn];void find(int x){    int i,j;    if (r[x]==0)    {        road[++num]=x;        return;    }    for (i=1;i<=500;i++)        if (f[x][i]!=0)        {            f[x][i]--; f[i][x]--;            r[x]--;    r[i]--;            find(i);                    }    road[++num]=x;}int main(){    int m,i,j,l;    freopen("fence.in","r",stdin);    freopen("fence.out","w",stdout);    scanf("%d",&m);    memset(r,0,sizeof(r));    for (i=1;i<=m;i++)    {        scanf("%d%d",&j,&l);        f[j][l]++;        f[l][j]++;        r[l]++; r[j]++;    }    for (i=1;i<=n;i++)        if (r[i]%2==1)        {            find(i);            break;        }    if (num==0)find(1);    for (i=num;i>=1;i--)cout<
          
           <